URAMARSITE (NH4, H3O)2(UO 2)2(AsO4, PO4)2 • 6H2O: A NEW MINERAL OF THE METAAUTUNITE GROUP

Abstract

New mineral uramarsite, a hydrous ammonium uranylarsenate, was found in the supergene zone of the Bota-Burum molybdenite–pitchblende deposit (southern Kazakhstan), which is made up of carbonatized felsite porphyry and tuff breccia. In the supergene zone, the uranium mineralization is represented by arsenate uranite; the molybdenum mineralization, by U-bearing powellite and less abundant wulfenite. According to Kopchenova and Skvortsova, the close association of pitchblende with fine-grained molybdenite, arsenopyrite, and pyrite in primary ores defined the specifics of supergene mineralization. At the initial stage of supergene zone formation, arsenates of Al and Fe (mansfieldite and pharmacosiderite) were formed under acid conditions in the arsenopyrite-rich zones. Uranites (uranospinite, sodium uranospinite, metazeunerite, chistyakovaite, and uramarsite) were formed at the last stage.